In the manufacture of vehicle tires, it is a common practice to make up a carcass for the tire, this carcass including substantially all of the tire except the outer circumferential reinforcing belts and tread package, at a first location and then transfer the carcass to a tire forming drum where the carcass is positioned for receiving a ring-shaped belt and tread package about the outer circumference of the carcass. The belt and tread package is made up separate from the carcass and therefore must be transferred from its manufacturing location to the location of the carcass and positioned thereupon precisely about the circumference of the carcass. The geometry of the belt and tread package and the fact that it must be placed about the outer circumference of the carcass only permits the package to be grasped about its outer circumference for effecting the transfer.
The operation of transferring of the belt and tread package onto the carcass is of great importance in the successful manufacture of a vehicle tire. First, it will be recognized that vehicle tires must be balanced for rotational stability when installed on a vehicle. This requires, among other things, that all of the components of the tire be uniformly positioned about the circumference of the tire. It further requires that the components be positioned precisely symmetrically about a plane which extends through the center of the tire between the opposite sidewalls thereof.
As noted, a common practice in the manufacture of vehicle tires is to make up the tire carcass at one location, make up the belt and tread package at a different and physically separated location, and then to marry these components at a third location. This general procedure allows one to precisely form the carcass to the desired tire size to provide the base upon which the tire is finally formed. However, this procedure places inordinate requirements upon the equipment which is required to transfer the belt and tread package onto the outer circumference of the carcass for the reasons that, first, the belt and tread package is a relatively flimsy ring and because of its make up it is also subject to deleterious deformation when grasped by a transfer ring. Second, the belt and tread package must be quickly and precisely positioned about the outer circumference of the carcass so that the package is symmetrically positioned about the carcass before the two components can be joined to form the tire precursor which later is placed in a mold for final formation of the tire and its tread. Commonly, in the industry the time allowed for the transfer of the belt and tread package onto the carcass is very short, for example a few seconds.
Transfer rings of the prior art include one or more outer rings which serve to mount and house a plurality of shoes, each of which is a arcuate segment of a circle, that are movable radially inwardly and outwardly of their housing. This radial movement of the shoes permits the shoes to be retracted radially outward for positioning of the transfer ring about a belt and tread package residing on its formation drum (belt and tread drum) and to be advanced radially inwardly for contacting and grasping the belt and tread package while it is still on its formation drum. Thereupon the formation drum is collapsed to leave the belt and tread package in the grasp of the transfer ring. In the formation of a belt and tread package on its formation drum, it is required that one or more of the several layer components of package be in tension in order to insure their proper placement in the package. This tension is released when the formation drum is collapsed so that the package in the transfer ring tends to contract a slight amount and to at least partially fall away from the grasp of the transfer ring. This movement of the package is more pronounced at the top of the package since the package is oriented vertically within the transfer ring, and presents a problem when attempting to position the package about the circumference of the carcass. Prior art transfer rings have no provision for accommodating this movement of the belt and tread package upon the collapsing of the formation drum.
Further, it is desired that the compressive force applied by the shoes of the transfer ring to the belt and tread package be sufficient to "round up" the belt and tread package within the transfer ring, but the force cannot be such as will deleteriously deform the package. In the prior art transfer rings, there is provided a single closing movement of the shoes of the transfer ring about the belt and tread package. The radially inward limit of movement of the shoes is set for a given size belt and tread package. Thus, the prior art does not provide means for accommodating any circumferential movement of the belt and tread package after it has been initially grasped by the transfer ring. Importantly, it is to be understood that nonuniform circumferential movement of the belt and tread package by as much as a few thousandths of an inch are most important in that these small movements prevent the belt and tread package from being positioned with its center axis coincident with the center axis of the carcass, thereby resulting in an unbalanced tire.
It is an object of the present invention to provide an improved transfer ring.
It is another object of the present invention to provide an improved transfer ring in which there is provision for adjusting the circumferential uniformity of the belt and tread package after it has been grasped by the transfer ring.
It is another object of the present invention to provide a method for the transfer of a belt and tread package onto a carcass in the course of the manufacture of a vehicle tire.